The present invention relates, in general, to a hydraulically operated release mechanism for a friction clutch assembly of motor vehicles, and more particularly to a hydraulic clutch release mechanism of a type having a slave cylinder (piston-cylinder unit) adapted for positioning in a clutch housing and having a pressure housing in concentric surrounding relation to a driveshaft and secured to a gearbox casing.
Activation of such a hydraulic clutch release mechanism is typically realized by a master cylinder which is manually actuated for supply of hydraulic fluid to the slave cylinder via a hydraulic pipe extending between the master cylinder and the slave cylinder. A simplified connection of the hydraulic pipe is realized by providing the clutch release mechanism in single-piece configuration with a pressure conduit which bridges a radial distance between the slave cylinder and the clutch housing, and has a free end provided with an adapter to which the hydraulic pipe is also connected.
A hydraulic clutch release mechanism of this type is described in U.S. Pat. No. 4,609,087, issued Sep. 2, 1986. The housing of this release mechanism is formed in one piece with the pressure conduit in the area of the flanged attachment zone of the gearbox casing, whereby the pressure conduit includes a passageway for hydraulic fluid and a separate vent passageway. The pressure conduit is so configured that the adapter as well as the ventilation project out through an opening of the clutch housing in assembled state, whereby the pressure conduit is received in a particular conduit guide of the clutch housing. For this purpose, the clutch housing is provided on one end with a U-shaped, radially inwardly directed channel which surrounds the end zone of the pressure conduit. Provided for sealing purposes is an elastic sealing element which is positioned in the clutch housing at a radial distance to the adapter and conforms to the U-shaped configuration of the channel to realize a sealing action. In view of its great length, the sealing element assumes also a support of the pressure conduit in the clutch housing. As the sealing element is disposed radially inwardly of the adapter at a distance thereto, contaminants may migrate into the space located radially outwardly of the sealing element between the pressure conduit and the wall surface of the clutch housing. Moreover, installation of the sealing element is complicated as a consequence of the dual function thereof because the sealing element must be pushed over the radially expanded adapter of the pressure conduit while increased care must be taken when axial joining the clutch housing and the gearbox casing. A further drawback of this conventional hydraulic clutch release mechanism is the need for a particularly designed clutch housing to suit the pressure conduit.